I'm currently 23 weeks and have been using a maternity belt for my morning runs for the past two weeks. I'm very happy with it - it supports my belly and seems to prevent that constant "gotta pee" feeling I had prior to wearing it. You should definitely check it out.
The belt I use is the cheap one from Motherhood that's only $15. It took me a couple of tries to figure out the right position for it, so if it doesn't feel good right away make sure it's not too tight or too high. I wrap mine so it's just above my hipbones on the sides and very low in the front.